The present invention relates, to a hydraulic damper for use in automotive suspension systems.
One of the hydraulic dampers of the type is disclosed, for example, in JP-A 10-141415. This hydraulic damper comprises an annular bush with a slit between a guide bush and a piston rod, and a coil spring arranged at the outer periphery of the bush to press the inner peripheral face of the bush against the piston rod, providing friction to rather low-speed movement of the piston rod.
However, the above hydraulic damper raises the following problem. The hydraulic damper aims to provide friction to rather low-speed movement of the piston rod, so that though received in a concavity formed in a rod guide with an axial clearance and axially retained by an anti-disengagement member covering the concavity, the bush is axially movable with respect to the rod guide due to presence of the clearance. Therefore, friction of the bush effectively operates on large-amplitude movement of the piston rod, but not on slight-amplitude movement or high-frequency vibrations since the bush moves axially together with the piston rod in within the clearance.
It is appreciated that control of slight-amplitude movement of the piston rod, e.g. high-frequency vibrations with amplitude of xc2x10.5 mm or less and frequency of 15 Hz or more, is one of the factors responsible for determination of the ride quality of automotive vehicles. However, the above hydraulic damper cannot reduce such high-frequency vibrations. Thus, there still remains a demand for a reduction both in low-frequency vibrations with rather low speed and large amplitude and in high-frequency vibrations.
It is, therefore, an object of the present invention to provide a hydraulic damper which contributes to an improvement in the ride quality of automotive vehicles by effectively reducing wide-ranging vibrations including high-frequency vibrations.
The present invention generally provides a hydraulic damper, comprising:
a cylinder filled with hydraulic fluid;
a piston slidably received in the cylinder through a piston ring;
a piston rod having one end mounted to the piston and another end extending outwardly of the cylinder;
a guide bush arranged on the side of the cylinder to slidably support the another end of the piston rod;
a seal member arranged outwardly with respect to the guide bush, the seal member slidably contacting the piston rod to prevent leakage of hydraulic fluid from the cylinder, the seal member comprising a lip portion; and
a friction member arranged inwardly with respect to the seal member, the friction member being mounted to one of the cylinder and the piston rod, the friction member slidably contacting another of the cylinder and the piston rod to produce friction greater than that produced at the seal member.
One aspect of the present invention is to provide a hydraulic damper, comprising:
a cylinder filled with hydraulic fluid;
a piston slidably received in the cylinder through a piston ring;
a piston rod having one end mounted to the piston and another end extending outwardly of the cylinder;
a guide bush arranged on the side of the cylinder to slidably support the another end of the piston rod;
a seal member arranged outwardly with respect to the guide bush, the seal member slidably contacting the piston rod to prevent leakage of hydraulic fluid from the cylinder, the seal member comprising a lip portion; and
a friction member arranged inwardly with respect to the seal member, the friction member being mounted to one of the cylinder and the piston rod, the friction member slidably contacting another of the cylinder and the piston rod to produce friction greater than that produced at the seal member, the friction member being arranged on the side of the cylinder in the vicinity of the guide bush to produce friction greater than that produced at the guide bush.
Another aspect of the present invention is to provide a hydraulic damper, comprising:
a cylinder filled with hydraulic fluid;
a piston slidably received in the cylinder through a piston ring;
a piston rod having one end mounted to the piston and another end extending outwardly of the cylinder;
a guide bush arranged on the side of the cylinder to slidably support the another end of the piston rod;
a seal member arranged outwardly with respect to the guide bush, the seal member slidably contacting the piston rod to prevent leakage of hydraulic fluid from the cylinder, the seal member comprising a lip portion; and
a friction member arranged inwardly with respect to the seal member, the friction member being mounted to one of the cylinder and the piston rod, the friction member slidably contacting another of the cylinder and the piston rod to produce friction greater than that produced at the seal member, the friction member is arranged on the side of the piston to produce friction greater than that produced at the piston ring.